Proper carb adjustment

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Oct 20, 2003 | 04:11 PM

serving_time

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From: North of Toronto, Ontario

Proper carb adjustment

Winter is on it's way up here in canada, and the ol' 6 started running a little rough this weekend early in the morning when it was the coldest out. I noticed that the carb was iceing up a little, so I know that I am gonna have to fab some sort of a heat riser to keep it warm. By the way, I have the stock 1bbl for the 6's.

My question is, what are the proper settings to have the carb set at so that I can get this thing running tops again.

Where should the idle mixture screw be?

What should idle speed be when warm?

What should idle speed be when cold and choke set?

Can I use a vacume guage to set/test any of the settings, and what are good vacume numbers to have?

Thanks for any help.

Oct 22, 2003 | 03:46 PM

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anybody know how to set up these things???????

Oct 22, 2003 | 08:09 PM

Lazy JW

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These things are so simple that I just do it all by ear. Idle speed until it sounds good, mixture in until too lean, out until too rich, back to halfway between, maybe a little closer to lean than rich. High idle fast enough to keep it running good until the choke comes off. You will definitely need some carb heat, these things can really ice up. Not very technical advice, but that's what I like about these engines.
Joe

Oct 23, 2003 | 04:00 PM

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Thanks Joe. That's about how I have it tuned now. I think my biggest problem is the iceing up over any adjustment. Guess it's back to the drawing board on some type of heat riser.

Oct 23, 2003 | 05:18 PM

Lazy JW

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I have headers on my 74 F-350 and have the Carter YF carb with stock air cleaner. I welded an appropriately sized tube to a header pipe with some air gap around the bottom and attached the stock type aluminum looking air tube up to the air cleaner. Had to use some carb cleaner in the little vacuum switch this fall as it gummed up and wouldn't close the Thermac door so it iced up on me one morning. I find that I have to re-adjust the carb seasonally, not too difficult though.
Joe

Oct 23, 2003 | 08:12 PM

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I don't have headers, but welding a tube to the side of the exhaust pipe and then drawing from it might be enough heat. So simple I never thought of it. Thanks.

Oct 24, 2003 | 03:25 AM

NM5K

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I would use the idle speed that is listed on the sticker, or in a manual. Will vary per tranny, year, etc...
Idle mixture, I slowly turn it in, until you see/hear a slight decrease in rpm. Then I turn it back out about a 1/2 turn. You can also use a vacuum gauge. Set for max vacuum. Should end up about the same place as I described using the rpm method. Not sure about fast idle. Check the sticker or a manual. I have a manual choke on mine, so my fast rpm is whatever I want it to be..

Yep, the vacuum gauge can be used to set mixture as mentioned. But I usually use the "rpm" drop method myself. I think it's more precise, as the vacuum will not change too much between the different mixtures. Will be hard to see a peak. Normal vacuum at idle should be in the 19-20-21 range. Not overly critical, and will vary per engine. Just as long as it's steady, and no quick regular dips due to valve problems, etc.. If it's steady at idle, you should be in pretty good shape. MK